1. Field of the Invention
The invention relates to cleaning apparatus and more particularly, to cleaning apparatus that contains a partitioned boil sump.
2. Description of the Prior Art
Conventional apparatus for cleaning objects, such as piece parts of manufactured goods, circuit boards, screws, bolts, nuts, and the like, typically use a multi-stage cleaning process in which an object is sequentially immersed in a series of chambers or tanks. Typically, these tanks contain a single solvent and, as such, the apparatus is known as a mono-solvent cleaning apparatus. Furthermore, conventional apparatus continuously cleanses the solvent during operation of the apparatus using a distilling process. Such distilling processes use a distinct boil sump to boil the solvent into a vapor and a condenser to condense the vapor into the solvent solution. The boil sump is generally separate from the tanks used for cleaning and rinsing an object.
Conventional solvents used for degreasing and cleaning metal and other non-absorbent objects include 1,1,1-trichloroethane, trichloroethylene, perchloroethylene, methylene chloride and the like. However, these solvents are suspected of depleting the earth's ozone layer. Consequently, so-called "ozone safe" solvents have recently been used in commercial cleaning apparatus. Illustratively, volatile solvents that are ozone safe include perflourocarbons (PFCs) and hydroflourocarbons (HFCs). Additionally, non-volatile, ozone safe solvents include hydrocarbon-based products such as dimethylsiloxane produced by DOW Chemical of Midland, Mich. and AXEREL produced by E. I. duPont de Nemours and Company of Wilmington, Del.
A typical cleaning apparatus using a multi-stage, single solvent cleaning process is disclosed in U.S. Pat. No. 4,886,082 issued Dec. 12, 1989 to S. Kato et al. (the '082 Kato et al. patent). This patent specifically teaches a three stage process by which objects are cleaned in three separate tanks of solvent.
To clean an object in accordance with the teachings of the '082 Kato et al. patent, the object is first placed in a vapor cleaning tank wherein a solvent is heated above its boiling point and the vapor of the solvent cleans the object. The object is not immersed in the solvent itself, but rather is positioned above the boiling liquid solvent.
After vapor cleaning for a pre-defined duration, the object is moved from the vapor cleaning tank to an ultrasonic cleaning tank. The vapor cleaning tank and the ultrasonic cleaning tank contain the same solvent. The object is immersed in the liquid solvent contained in the ultrasonic cleaning tank and ultrasonic transducers located at the bottom of the tank apply ultrasonic waves to the solvent. As is well known in the art, ultrasonic cavitation of the solution caused by the ultrasonic waves removes particulate material from the object.
Lastly, the cleaning process taught by the '082 Kato et al. patent teaches immersing the object into a liquid solvent in a rinse tank. The solvent contained in the rinse tank is the same solvent as that used in the vapor cleaning and ultrasonic cleaning tanks. The object, now that it is clean, is then removed from the cleaning apparatus and air dried.
To continuously cleanse the solvent while it is used in the cleaning apparatus, the '082 Kato et al. patent teaches continuously removing a portion of the solvent from the vapor cleaning tank and channeling the removed solvent to a separate distilling tank, also known in the art as a boil sump. In the distilling tank, the solvent is heated to a boil to produce solvent vapor. A condenser, located above the distilling tank and maintained at a temperature substantially below the boiling point of the solvent, condenses the solvent vapor into a solution. The solvent solution is channeled from the condenser into the rinse tank. The rinse tank is separated from the ultrasonic tank by a spillway that enables the solvent from the rinse tank to overflow into the ultrasonic cleaning tank. A conduit connects the ultrasonic tank to the vapor cleaning tank to provide solvent thereto. Lastly, the vapor cleaning tank is connected, via a conduit, to the distilling tank. As such, a closed system is produced that requires the solvent to sequentially circulate through each of the tanks and ultimately be boiled in the distilling tank before recirculation. Therefore, particulate contaminants, grease and oil contained in the solvent solution are continuously removed from the solvent by the distilling process and those contaminants remain in the distilling tank.
The '082 Kato et al. patent teaches using a distinct distilling tank that is separate from the cleaning and rinsing tanks. To reduce the footprint of the cleaning apparatus and, also, simplify the overall design thereof, it would be advantageous to have a single tank that can be used for both ultrasonic cleaning of objects and distilling the solvent, i.e., an integrated cleaning and distilling tank.
Furthermore, in cleaning some objects, a single solvent is not sufficient and two different solvents, i.e., co-solvent cleaning, must be used to facilitate complete cleansing of the object. For example, some types of grease and oils are best removed by a non-volatile hydrocarbon-based solvent. However, such non-volatile solvents do not dry very quickly and may not remove all forms of contaminants from the object. Moreover, when air dried, a non-volatile solvent may leave a solid residue on the object. Therefore, a second solvent, typically a volatile solvent, is used to remove the residual non-volatile solvent from the object and also remove any remaining oils, greases or particulate matter not removed from the object by the non-volatile solvent. Advantageously, volatile solvents dry by evaporation in a relatively short period of time. Thus, a co-solvent cleaning process removes a variety of particulate matter, grease and oil from an object as well as produce a dry object within a relatively short period of time. Thus, it would be also advantageous to have a cleaning apparatus that is capable of both mono-solvent and co-solvent cleaning operations.
Therefore, a need exists in the art for a single cleaning apparatus having a distilling tank that is an integral portion of the cleaning tank and that performs both mono-solvent and co-solvent cleaning.